PVC compositions are well known in the art (see, for example, U.S. Pat. Nos. 6,063,846 and 6,608,142 and U.S. patent publication number 2005/0203230), and typically comprise PVC and at least one other polymer, e.g., a polyolefin, a styrenic polymer, etc. Since many of these other polymers are typically not miscible or otherwise compatible with PVC, often these compositions also include a compatibilizer, e.g., chlorinated polyethylene. PVC compositions that do not contain a plasticizer tend to be rigid and are suitable for the manufacture of rigid products such as pipe and tubing. PVC compositions that include a plasticizer tend to be flexible and are suitable for use in such applications as wire and cable insulation and jacketing, and medical device components. Examples of such compositions include the FLEXALLOY® products available from Teknor Apex.
Phthalic acid diesters (also known as “phthalates”) are known plasticizers for PVC and other vinyl polymers. Examples of common phthalate plasticizers include di-isononyl phthalate (DINP), diallyl phthalate (DAP), di-2-ethylhexyl-phthalate (DEHP), dioctyl phthalate (DOP) and diisodecyl phthalate (DIDP). Other common plasticizers, used for high temperature applications, are trimellitates and adipic polyesters. Mixtures of plasticizers are often used to obtain optimum properties. Phthalate plasticizers have recently come under intense scrutiny by public interest groups that are concerned about the negative environmental impact of phthalates and potential adverse health effects in humans (especially children) exposed to phthalates.
Flexible PVC compositions made with plasticizers that are derived from renewable sources (i.e., biochemical plasticizers) are an alternative to petrochemical-based plasticizers. However, biochemical plasticizers can be inferior in certain respects to compositions made with plasticizers not derived from renewable sources (e.g., phthalate or trimellitate plasticizers) because they are insufficiently compatible with the PVC or because they have poor heat-aging properties. These disadvantages have limited the use of biochemical plasticizers, such as epoxidized soybean oil, to secondary plasticizers, lubricants or stabilizers, which are present in only small quantities in PVC-based compositions.